Ion transport membrane devices require metal conduit to ceramic conduit transitions. Typically, the ceramic ion transport membrane device will need to be coupled to a metallic piping system to convey the permeate side product to the next process operation. It is neither economically nor mechanically practical to use the same ceramic material for this piping system as is used in the membranes. The transition from metal to ceramic must remain sufficiently leak-free in spite of substantial changes in operating temperature, pressure, and gas composition. Thus, a seal between the metal conduit and the ceramic conduit is required that will accommodate the large differences in coefficients of thermal expansion and chemical expansion, and also provide robust performance over long periods of operation at temperatures in excess of 800° C. and pressures of up to about 2.5 MPa (absolute) (350 psig), the pressure difference providing a compressive force on the seal. The seal must be able to provide sealing at both high pressure and low pressure. It is also necessary that the seal components in contact with the metal and ceramic parts be chemically compatible with these parts.
While particularly suited for ion transport membrane devices, the seal between a ceramic part and a metal part described herein may find applicability to other technologies that operate at similar temperatures and pressures and require sufficiently leak-free sealing.
U.S. Pat. No. 7,222,406, incorporated herein by reference, discloses multi-layer seals in which a gasket body with compliant interlayers positioned adjacent each side of the gasket body; the gasket body is sandwiched between two compliant interlayers.
However, issues can arise when a compliant interlayer is in contact with the ceramic. Adhesion of the compliant interlayer to the ceramic can lead to mechanical stresses in the ceramic and possible breakage. Chemical reaction between the compliant interlayer and the ceramic or diffusion of the compliant interlayer into the ceramic can lead to undesirable property changes of the ceramic.
Industry desires a seal between ceramic conduits and metal conduits that are sufficiently leak-tight and durable.